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Inside the Machine

Open the case and meet the hardware. Learn what the CPU, RAM, ROM and storage each do, and how the fetch-decode-execute cycle runs your programs.

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What you'll cover

Open the case 💻

A computer is a team of hardware parts working together: one part **processes**, others **remember**, others **store** for the long term. Learn what each part does, and you can explain exactly how a program runs.

The main components 🗂️

Four parts do most of the work:

Match each component to its job

  • CPU
  • RAM
  • ROM
  • SSD
  • Processes the program instructions
  • Temporary working memory, lost when off
  • Holds permanent start-up instructions
  • Stores files permanently

Which is volatile?

Which type of memory is volatile, meaning it loses its contents when the power is turned off?

  • RAM
  • ROM
  • An SSD
  • A hard disk

The CPU never stops 🧠

The **CPU** (Central Processing Unit) runs programs by repeating the **fetch-decode-execute cycle**. It **fetches** the next instruction from memory, **decodes** what it means, then **executes** it, billions of times a second.

The fetch-decode-execute cycle

An interactive activity.

RAM versus ROM 💡

The key contrast: **RAM is volatile** (contents lost when powered off) and holds whatever is running now. **ROM is non-volatile** (keeps its contents) and holds the fixed start-up instructions. More RAM lets a computer run more programs at once.

True or false

Select the TWO true statements about hardware.

  • The CPU carries out the fetch-decode-execute cycle
  • RAM loses its contents when the power is turned off
  • ROM is where you save your documents
  • An SSD is a type of input device

Match each part of the CPU to its role

  • ALU
  • Control Unit
  • Register
  • Cache
  • Does calculations and logic
  • Directs the flow of data
  • Tiny, very fast storage inside the CPU
  • Fast memory holding frequently used data

Making it faster

A CPU runs faster with a higher _____ speed, more processing _____, and a larger _____ to hold frequently used data.

clock cores cache screen colours speaker

Diagnose the machine

An interactive activity.

Hardware frame

The _____ runs programs using the fetch-decode-execute cycle. _____ is volatile working memory, while ROM is _____ and holds start-up instructions. Files are kept on secondary _____, such as an SSD.

CPU RAM non-volatile storage ROM ALU volatile input

Explain the machine

An interactive activity.